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Fulltext Combating Parasitic Nematode Infections, Newly Discovered Antinematode Compounds from Marine Epiphytic Bacteria

Salikin NH, Nappi J, Majzoub ME, Egan S

Microorganisms, 2020 Dec 11;8(12).
PMID: 33322253 DOI: 10.3390/microorganisms8121963

Parasitic nematode infections cause debilitating diseases and impede economic productivity. Antinematode chemotherapies are fundamental to modern medicine and are also important for industries including agriculture, aquaculture and animal health. However, the lack of suitable treatments for some diseases and the rise of nematode resistance to many available therapies necessitates the discovery and development of new drugs. Here, marine epiphytic bacteria represent a promising repository of newly discovered antinematode compounds. Epiphytic bacteria are ubiquitous on marine surfaces where they are under constant pressure of grazing by bacterivorous predators (e.g., protozoans and nematodes). Studies have shown that these bacteria have developed defense strategies to prevent grazers by producing toxic bioactive compounds. Although several active metabolites against nematodes have been identified from marine bacteria, drug discovery from marine microorganisms remains underexplored. In this review, we aim to provide further insight into the need and potential for marine epiphytic bacteria to become a new source of antinematode drugs. We discuss current and emerging strategies, including culture-independent high throughput screening and the utilization of Caenorhabditis elegans as a model target organism, which will be required to advance antinematode drug discovery and development from marine microbial sources.
Assessment of cultivation parameters influencing pectinase production by Aspergillus niger LFP-1 in submerged fermentation

Mat Jalil MT, Zakaria NA, Salikin NH, Ibrahim D

J Genet Eng Biotechnol, 2023 Apr 24;21(1):45.
PMID: 37093363 DOI: 10.1186/s43141-023-00510-z

BACKGROUND: Pectinase is helpful in food and beverage industries, particularly in the preparation of fruit juice, the extraction of vegetable oil, and the fermentation of coffee. The current work aimed to screen Aspergillus niger LFP-1, a recently identified fungal strain, for its ability to produce pectinase and to ascertain the contribution of various physicochemical factors to pectinase production.
RESULTS: The primary and secondary pectinase activity screenings by Aspergillus niger LFP-1 were performed using pectin screening agar and shake flask system, respectively. The finding revealed that the locally isolated strain is able to secrete favourable pectinase production. Before improvement, the pectinase production was 0.88 ± 0.09 U/mL. However, the improved conditions such as 6 days of the cultivation period, agitation speed of 150 rpm, inoculum size of 1 × 106 spores/mL, 2.5% (w/v) citrus pectin, and 0.4% (w/v) ammonium nitrate could significantly increase pectinase production up to 7.41 ± 0.24 U/mL, representing an 88% increase. In this study, supplementing 2.5% (w/v) citrus pectin to the culture medium as a carbon source increased enzyme production by up to 3.07 ± 0.17 U/mL. Meanwhile, 0.4% (w/v) ammonium nitrate was used as a nitrogen source yielding the highest enzyme activity with a value of 6.86 ± 0.07 U/mL.
CONCLUSION: Thus, the locally isolated fungal strain, A. niger LFP-1 has outstanding pectinase-producing capability and can be utilized for the commercial production of pectinase. The improved cultural conditions significantly increase pectinase production and shorten the incubation period from 8 days (before improvement) to 6 days (after improvement).
Novel Nematode-Killing Protein-1 (Nkp-1) from a Marine Epiphytic Bacterium Pseudoalteromonas tunicata

Salikin NH, Dubois M, Nappi J, Lebhar H, Marquis C, Egan S

Biomedicines, 2021 Oct 30;9(11).
PMID: 34829814 DOI: 10.3390/biomedicines9111586

Drug resistance among parasitic nematodes has resulted in an urgent need for the development of new therapies. However, the high re-discovery rate of anti-nematode compounds from terrestrial environments necessitates a new repository for future drug research. Marine epiphytes are hypothesised to produce nematicidal compounds as a defence against bacterivorous predators, thus representing a promising yet underexplored source for anti-nematode drug discovery. The marine epiphytic bacterium Pseudoalteromonas tunicata is known to produce several bioactive compounds. Screening heterologously expressed genomic libraries of P. tunicata against the nematode Caenorhabditis elegans, identified as an E. coli clone (HG8), shows fast-killing activity. Here we show that clone HG8 produces a novel nematode-killing protein-1 (Nkp-1) harbouring a predicted carbohydrate-binding domain with weak homology to known bacterial pore-forming toxins. We found bacteria expressing Nkp-1 were able to colonise the C. elegans intestine, with exposure to both live bacteria and protein extracts resulting in physical damage and necrosis, leading to nematode death within 24 h of exposure. Furthermore, this study revealed C. elegans dar (deformed anal region) and internal hatching may act as a nematode defence strategy against Nkp-1 toxicity. The characterisation of this novel protein and putative mode of action not only contributes to the development of novel anti-nematode applications in the future but reaffirms the potential of marine epiphytic bacteria as a new source of novel biomolecules.
Combating multidrug-resistant (MDR) Staphylococcus aureus infection using terpene and its derivative

Salikin NH, Keong LC, Azemin WA, Philip N, Yusuf N, Daud SA, et al.

World J Microbiol Biotechnol, 2024 Dec 04;40(12):402.
PMID: 39627623 DOI: 10.1007/s11274-024-04190-w

Multidrug-resistant (MDR) Staphylococcus aureus represents a major global health issue resulting in a wide range of debilitating infections and fatalities. The slow progression of new antibiotics, limited choices for treatment, and scarcity of new drug approvals create immense obstacles in new drug line development. S. aureus poses a significant public health risk, due to the emergence of methicillin-resistant (MRSA) and vancomycin-resistant strains (VRSA), necessitating novel antibiotics for effective control management. Current studies are delving into the terpenes' potential as an antimicrobial agent, indicating positive prospects as promising substitutes or complementary to conventional antibiotics. Concurrent reactions of terpenes with conventional antibiotics create synergistic effects that significantly enhance antibiotic efficacy. Accumulated evidence has shown that while efflux pump (e.g., NorA, TetK, and MepA) is revealed as an essential defense of S. aureus against antibiotics, terpene and its derivative act as its potent inhibitor, suggesting the promising potential of terpenes in combating those infectious pathogens. Furthermore, pronounced cell membrane disruptive activity and antibiofilm properties by terpenes have been exerted, signifying their significance as promising prevention against microbial pathogenesis and antimicrobial resistance. This review provides an overview of the potential of terpenes and their derivatives in combating S. aureus infections, highlighting their potential mechanisms of action (MOA), synergistic effects with conventional antibiotics, and challenges in clinical translation. The unique properties of terpenes offer an opportunity for their use in developing an exceptional defense strategy against antibiotic-resistant S. aureus.